Bismuth subsalicylate: history, chemistry, and safety.

Pepto-Bismol, which contains bismuth subsalicylate (BSS) as the active ingredient, has been marketed in the United States for more than 80 years. In the gastrointestinal tract, BSS is converted to salicylic acid and insoluble bismuth salts. The salicylate portion of BSS is extensively absorbed (greater than 90%) and excreted in urine. The maximal daily dose of Pepto-Bismol (4.2 g of BSS) results in peak concentrations of salicylate in plasma considerably below the level of salicylate toxicity. In contrast, little bismuth from BSS is absorbed from the gastrointestinal tract (less than .005%). Extended dosing of Pepto-Bismol (3.14 g of BSS/d) for up to 6 weeks produced a mean concentration of bismuth in blood of 16.1 +/- 7.9 ng/g, considerably below concentrations in blood that have been reported to cause neurotoxicity. Neurotoxicity studies in animals and human safety data indicate that Pepto-Bismol can be used safely for its acute indications and for up to 3-4 weeks of extended dosing.